1. Field of the Invention
The present invention relates to an ink cartridge which is to be used with an ink-jet recording apparatus and is constructed so as to feed ink to a recording head. The present invention also relates to an ink-jet recording apparatus using the ink cartridge.
2. Description of the Related Art
An ink-jet recording apparatus produces comparatively low noise during printing operation and can form small dots at high density. Hence, the ink-jet recording apparatus has recently been used in a number of printing applications, including color printing.
Such an ink-jet recording apparatus is usually equipped with an ink-jet recording head which is mounted on a carriage and moved in the widthwise direction of recording paper, and paper feed means for moving the recording paper in the direction orthogonal to the traveling direction of the recording head. On the basis of print data, ink droplets are ejected from the recording head, thus recording the data on the recording paper.
The recording head is mounted on the carriage, and is capable of ejecting ink droplets of, for example, black, yellow, cyan, and magenta. Accordingly, the ink-jet recording apparatus enables full-color printing by changing the proportions of ink types, as well as effecting text printing with black ink.
Incidentally, in order to effect a comparatively-high volume of printing, a recording apparatus of this type supplied for, for example, an office or business purpose, requires use of high-volume ink cartridges. To this end, there has been provided a recording apparatus, in which ink cartridges are fitted to a cartridge holder provided, for example, to an apparatus main body.
In the recording apparatus, sub-tanks are disposed on the carriage having the recording head, and the respective sub-tanks are replenished with ink from corresponding ink cartridges by way of ink supply tubes. The sub-tanks, in turn, supply ink to the recording head.
Recently, growing demand exists for a large-size recording apparatus capable of effecting printing on larger-size paper, in which a carriage travels a longer scan distance. In order to improve throughput of such a recording apparatus, a larger number of nozzles are provided in a recording head.
Further, demand exists for a recording apparatus which sequentially supplies ink to the respective sub-tanks mounted on the carriage from corresponding ink cartridges while performing printing operation, in order to improve throughput, and which stably supplies ink from the respective sub-tanks to the recording head.
In such a recording apparatus, since the carriage travels over a longer scan distance, the lengths of respective ink supply tubes inevitably increase. Further, as mentioned above, a larger number of nozzles are provided in the recording head. Hence, such a recording apparatus encounters a technical problem of deficient ink supply to the sub-tanks because the recording head consumes a large quantity of ink, and an increase in the dynamic pressure (i.e., pressure loss) of ink is likely to occur within each of the ink supply tubes interconnecting the ink cartridges and the sub-tanks.
As one measure to prevent this technical problem, there may be employed, for example, a construction in which air pressure is applied to the ink cartridges to forcibly inducing ink flows from the ink cartridges to the sub-tanks under air pressure. This construction makes it possible to supply a sufficient amount of ink to the sub-tanks.
FIG. 36 is a cross-sectional view showing an example construction of a related-art ink cartridge utilized for such an ink-jet recording apparatus. In FIG. 36, reference numeral 81 designates a case defining the outer shell of an ink cartridge. The case 81 is integrally formed, into a shape of a bottle having a relatively large opening, from synthetic resin material by means of blow molding (hollow molding).
A columnar cap member 84 is fitted into an opening section 82 by way of an O-ring 83. By means of the cap member 84 and the O-ring 83, the inside of the case 81 is sealed, thus constituting a pressure chamber 85 within the case 81.
An ink outlet section 86 employing a ball valve is formed in the center of the columnar cap member 84. Ink can be led out from an ink pack 87—which is housed in the case 81 and formed from ink-filled flexible material—to the outside via the ink outlet section 86.
An air inlet port 89 is formed in a portion of the cap member 84. A rubber plug 88 is fitted on the air inlet port 89. A through hole 88a is formed in the center of the rubber plug 88. When the ink cartridge is not attached to an ink-jet recording apparatus, the through hole 88a is closed.
When the ink cartridge is attached to the recording apparatus, an unillustrated hollow needle provided on the recording apparatus penetrates through the through hole 88a of the rubber plug 88, and pressurized air can enter the pressure chamber 85 by way of the hollow needle.
Consequently, the pressurized air is introduced into the pressure chamber 85 by way of the hollow needle. Upon receipt of pressure, the ink contained in the ink pack 87 is led to the outside by way of the ink outlet section 86.
The above ink cartridge of related-art construction involves several problems to be solved, as described below.
A first problem is as follows: In the ink cartridge of the related-art construction mentioned above, the case forming the outer shell is integrally formed by blow molding, and consequently, as can be seen from the exemplified construction shown in FIG. 36, the ink pack 87 is integrally attached to the columnar cap member 84 formed with the ink replenishing valve 86 and the air introducing valve 88.
The cap member 84 is pressure-fitted to the opening section 82 using the O-ring 83 so that the ink pack 87, which has not been filled with ink, is inserted into the case 81. Subsequently, ink is injected into the ink pack 87 from the exterior via the ink replenishing valve 86 to thereby complete a product, i.e. the ink cartridge.
Since the case defining the outer shell of the ink cartridge of related-art construction is integrally formed by blow molding, difficulty is often encountered in assembling an ink pack, which has already filled with ink, into the case. That is, the ink pack must be filled with ink in a subsequent process.
Further, predetermined pressure is imposed on the inside of the case during the recording operation of the recording apparatus. There must be employed a countermeasure for preventing deformation of the case, which would otherwise be caused when the case receives the pressure. For this reason, in order to ensure the strength of the case, adoption of a simple construction, such as a cylindrical shape like a bottle having a relatively large opening section as shown in FIG. 36, is preferable.
However, such an outer shell yields a problem of an increase in the occupation volume of the case, resulting in difficulty in designing the layout of a recording apparatus of this type, which requires parallel arrangement of color ink cartridges.
Another conceivable measure for ensuring the strength of the case is to increase the thickness of the case. However, a large quantity of synthetic resin material is consumed for forming a case, thus posing difficulty in contributing to conservation of resources.
In contrast, another conceivable measure for reducing the quantity of synthetic resin material consumed is to integrally form reinforcement ribs on a part of the case. However, as mentioned above, when blow molding is employed for forming a case, forming reinforcement ribs in the interior of the case is usually difficult.
A second problem is that, in a case where ink cartridges of related-art construction attached to a recording apparatus are removed from the recording apparatus after having performed ink supply operation, the through hole 88a formed in the rubber plug 88 is closed immediately due to elasticity of rubber, thereby leaving pressurized air within the pressure chamber 85.
The pressurized air remaining in the pressure chamber 85 continues pressurizing the ink pack 87.
If the ball constituting the ink outlet section 86 is pushed unintentionally or intentionally through use of, for example, a pen tip or similar implement, the ink contained in the ink pack 87 gushes forth, thereby soiling the surrounding areas.
Another problem is that ink may leak out from the ink outlet section 86 even when the pushing action is not performed.
In order to prevent occurrence of such problems, there must be taken measures for actively letting the air pressure escape from the inside of the pressure chamber 85, by inserting a hollow needle, such as an injection needle, into the through hole 88a of the rubber plug 88 when the ink cartridge is removed from the recording apparatus.
However, such an operation for releasing pressure is cumbersome for the user, and this is not the reliable countermeasure in practice.
Even when the ink cartridge of related-art construction is stored without being attached to the recording apparatus, the ambient temperature change of the location where the ink cartridge is stored, particularly, the ambient temperature increase causes the internal atmospheric pressure of the pressure chamber 85 to increase. Accordingly, ink leaks out from the ink outlet section 86.
A natural approach is to construct an ink cartridge which supplies ink by introducing pressurized air into a case, such that the inside of the case is held hermetic over a long period of time during actual use of the ink cartridge. In addition, consideration of ease of assembly and ease of disassembly and recycling is particularly important. Fulfillment of these requirements is sought strongly.
When primarily text data are to be printed, the ink-jet recording apparatus utilizing the ink cartridge of such construction employs black ink, as is well known. When color printing is to be effected, color inks, such as yellow ink, magenta ink, and cyan ink, are used.
As set forth, the ink is available while an ink pack formed from flexible material in the form of a bag is filled with ink and the ink pack is housed in a cartridge case defining the outer shell of the ink cartridge. The ink cartridges are formed so as to assume substantially identical outer shapes. Further, the ink cartridges are filled with substantially-identical amounts of ink.
In a case where the majority of printed matter to be produced by a recording apparatus is, for example, text data, the amount of color ink used and the frequency of use of color ink are low. Hence, the color ink cartridges will become empty considerably later than will a black ink cartridge.
For this reason, expiration dates of color ink arrive before the color ink cartridges become empty, thus involving replacement of the ink cartridges with new ink cartridges.
Conversely, when the recording apparatus is used for printing a large number of color images, the amount of black ink used and the frequency of use of black ink are low. The black ink cartridge will become empty much later than will the color ink cartridges. Hence, the expiration date of black ink arrives while black ink still remains in the cartridge.
Thus, in addition to a problem of imposing running costs on the user, there arises another problem of a load of disposing of a considerable amount of ink remaining in an ink cartridge which itself is to be disposed of.
A conceivable measure for diminishing running costs and the load of disposing of ink is to provide an ink cartridge filled with a smaller amount of ink. In this case, there may be adopted regulation means for diminishing the amount of ink contained in an ink pack.
For convenience of attaching a cartridge into a holder of a recording apparatus, the outer shell of an ink cartridge case for housing an ink pack must be of a certain size and shape, regardless of the volume of ink. In an ink cartridge filled with a smaller amount of ink, a large gap arises between the cartridge case and the ink pack.
For example, in the event that an ink pack is freely moved within the cartridge case because of vibration stemming from transport of an ink cartridge; particularly, in the event that the ink pack has experienced excessive physical shock, the ink pack will be broken.
Another conceivable measure to prevent breakage of an ink pack is to make the outer dimensions of cartridge cases identical and to change the internal size and shape of the case in accordance with the amount of ink to be contained. In a case where an attempt is made to adopt such a measure, metal molds to be used for molding ink cartridge cases must be prepared separately for a high-volume ink cartridge and for a low-volume ink cartridge, and costs of the metal molds are reflected in manufacturing costs.
In connection with a recording apparatus which is constructed so as to push ink from an ink cartridge by means of pressurized air and which enables selective use of high-volume ink packs and low-volume ink packs, when low-volume ink cartridges are used, a large amount of pressurized air must be introduced into the cartridge cases.
Consequently, for example, when an attempt is made to activate the recording apparatus by turning on the operating power of the recording apparatus, consumption of a considerable amount of time is required before the recording apparatus becomes able to print, thereby deteriorating the throughput of the recording apparatus.